Connection diagram of an indirect heating boiler

Indirect boiler connection diagram

The hot walls of the coil transfer heat to the cold water, which at the outlet already has a temperature suitable for taking a shower. Also indirect heating boilers differ in automatic control, it is either absent at all, or attached to the hinged installation, or built into the boiler itself. Also look for a wiring diagram of the boiler to the boiler. For example, you have a pump and you need to turn it off when you turn off the boiler. Usually you need to take two conductors from the boiler and lead it to the thermostat on the boiler relay: The boiler’s two DHW conductors can have a simple AC voltage of volts.

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How to properly connect an indirect heating boiler And here’s the thing to understand: Almost all indirect heating boilers use a changeover contact and can be used as a dry contact. A detailed wiring diagram of the indirect water heater Also in each branch connection ball shutoff valves are installed. Two are fed hot water, one. cold water. If you are not happy with the change in temperature in the boiler, which varies over time and have to readjust the mixer. The pump is turned on by the thermostat in the boiler.

There are, of course, many different valves and many different signals on the operation of heating circuits. The first have a fitting to mount on the wall, the second such fittings do not have, but have a stand to mount on the floor in the boiler room. Connection with recirculation The scheme of connection of the indirect heating boiler with recirculation involves the following convenience. you open the faucet, and from it immediately begins to flow hot water. Binding gas boiler and indirect water boiler polypropylene

What you need to know when connecting the boiler

Boiler devices can operate two water heating circuits.

  • The first is the water in the heating system, which after being heated is supplied to the heating radiators. Such a circuit may be closed and special chemical additives may be added to such water in order to ensure continuous operation of radiators, cleaning systems from scaling and so on.
  • The second circuit is the water used for domestic purposes. It is designed for washing dishes, for washing. Consequently, this circuit is open circuit. Cold water flows into it from the main water supply system, and then, as it is used, such water is discharged into the sewer.

Connection principles of boiler fitting

When installing strapping system boiler indirect heating must remember the following principles:

  • The point of entry of cold water into the boiler harness should be at the lowest point of the system, but the hot water comes out of the harness at the top point.
  • The recirculation point is therefore practically in the geometric center of the piping.

When complying with these principles of installation piping work the heating system will be most effective and the heat from the boiler will be efficiently transferred to the mass of incoming water.

Wiring rules

Wiring and piping is simplified when the boiler is installed simultaneously with the heating unit, pumping equipment and other elements necessary to assemble the DHW network. In a previously arranged system it is somewhat more difficult to install the BKN.

For efficient operation of the boiler, the following rules should be observed

  • The installation point is selected at a minimum distance from the boiler;
  • a flat surface is created for installation;
  • to prevent damage from thermal expansion, a hydraulic accumulator is installed on the outlet pipe of hot water, its volume is taken from 10% of boiler capacity;
  • The circuits are equipped with valves;
  • Check valves are installed to prevent a back flow of water;
  • To improve water purity, mechanical filters are cut into the supply pipe;
  • A pump or pump group must be installed.

Hinged BCH cannot be mounted on wooden or plasterboard walls. only on solid brick or concrete walls. Brackets and other types of fasteners are fixed by dowels, anchors, staples.

Regardless of the method of location (wall or floor), the boiler must be installed at the same level or higher than the associated boiler. Floor standing models can be mounted on a concrete foundation or a stable base up to 1 m high.

During installation the pipes are led away to the side of heater or hidden behind it behind the false wall. Do not use corrugated hoses to connect: they will not withstand the pressure of water.

The strapping includes the following functional elements

  • pressure and circulation pumps;
  • mechanical filter;
  • reducer
  • check valve;
  • diaphragm tank with safety valve;
  • three-way mixer;
  • two-way thermostat;
  • heat exchanger with flow-through (optional).
connection, diagram, indirect, heating, boiler

What is an indirect water heater and what they are

A water heater or indirect water heater is a tank with water in which a heat exchanger is placed (coil or water jacket type. cylinder in cylinder). The heat exchanger is connected to the heating boiler or any other system in which hot water or other coolant is circulating.

Heating is simple: hot water from the boiler passes through the heat exchanger, it heats the walls of the heat exchanger, and they, in turn, transfer the heat to the water in the tank. Since the heating is not direct, this water heater is called “indirect heating”. Heated water is used for household needs as needed.

One of the important details in this design is a magnesium anode. It reduces the intensity of corrosion processes. the tank lasts longer.

There are two types of indirect heating boilers: with built-in control and without. Indirect heating boilers with built-in control are connected to the heating system, operating from boilers without control. They have a built-in temperature sensor, its own control that turns on / off the supply of hot water in the coil. When connecting this type of equipment, all that is needed is to connect the heating flow and return flow to the appropriate inputs, connect the cold water supply and connect the hot water distribution pipe to the upper output. That’s all, you can fill the tank and start heating it.

Conventional indirect heating boilers work mainly with automated boilers. During installation, it is necessary to install the temperature sensor in a certain place (there is a hole in the body) and link it to a certain input of the boiler. Further make strapping indirect heating boiler in accordance with one of the schemes. You can connect them and energy-independent boilers, but this requires a special circuit (see below).

That it should be remembered that the water in the indirect heating boiler can be heated just below the temperature of the coolant circulating in the coil. So if you have a low-temperature boiler and gives out, say, 40 ° C, the maximum temperature of water in the tank will be so. you can not heat it in any way. To get around this limitation, there are combined water heaters. They have a coil and built-in heating element. The main heating in this case comes from the coil (indirect heating), and the heater only brings the temperature to a predetermined. Also, such systems are good in combination with solid fuel boilers. the water will be warm even when the fuel is burned.

What else can be said about the peculiarities of construction? In large volume indirectors are installed several heat exchangers. this reduces the time of water heating. For reduction of time of heating of water and for slower cooling down of a tank, it is better to choose models with heat isolation.

What boilers can be connected to

Boilers of indirect heating can work with any source of hot water. Suitable any water-heating boiler. solid fuel. on wood, coal, briquettes, pellets. You can connect any type of gas boiler, electric or liquid fuel boiler.

Scheme of connection to a gas boiler with a special outlet for an indirect heating boiler

Simply, as written above, there are models with their own control, and then their installation and piping is a simpler task. If the model is simple, you have to think through a system of temperature control and switching the boiler from heating radiators to heating hot water.

The forms of tanks and installation methods

The indirect heating boiler can be installed on the floor, can. mounted on the wall. Wall-mounted variants have a capacity of no more than 200 liters, and floor standing variants can hold up to 1500 liters. In both cases, there are horizontal and vertical models. When installing the wall version, the mounting is standard. brackets, which are mounted on wall plugs of the appropriate type.

If we talk about the shape, then most often these devices are made in the form of a cylinder. Almost all models have all the working conclusions (outlets for connections) derived from the back. It is easier to connect, and the appearance is better. On the front of the panel there are places to install a temperature sensor or thermostat, some models have the ability to install a heating element. for additional reheating of water if there is not enough heating power.

According to the type of installation they are wall and floor, the capacity. from 50 liters to 1500 liters

When installing the system, it is worth remembering that the system will only work effectively if the boiler capacity is sufficient.

Wiring rules

BCH is simultaneously connected to the heating system and hot and cold water pipes. The best option. is the installation of such water heater along with all the other equipment, including the boiler unit, which can operate on any fuel. The process is more complicated if it is decided to improve the system, by installing BKN after the start of the thermal circuit of the house.

The efficiency of water treatment for DHW will be ensured if certain rules are observed when connecting the indirect water heater:

  • the installation of the heater must be carried out at a minimum distance from the boiler;
  • Mandatory equipping of the supply pipeline filter for water purification from impurities;
  • floor water heating device for hot water must be installed on a flat horizontal surface;
  • All pipe circuits must be equipped with shut-off valves;
  • it is recommended to install a hydraulic tank with a capacity of at least 10% of the boiler volume on the hot water outlet to reduce the possibility of damage due to thermal expansion;

Note! Often the hot water preparation system for water supply is equipped with a separate pump or an entire pump group to ensure and even control the speed of medium movement through the pipes.

Do not hang the HKH on an unstable partition wall. Tanks are installed only on solid walls of reinforced concrete or brick. Fix the fastening elements with special fasteners. They are matched to the material of the building structure.

Installation of the indirect heating boiler can be performed on the floor. it is also hanged on the wall. Regardless of the installation site, the tank is installed above or at the level of the boiler. Floor standing heating tanks are mounted on a solid base. This can be a concrete foundation. Depending on the installation site, a stable base is also used. Their height should not exceed 1 m.

Please note! Inlet and outlet pipes are recommended to lead away to the side or behind the tank, hiding them behind a false wall. Never use corrugated hoses for connections. The reason is their inability to withstand the high pressure of water.

  • circulating pump units;
  • Two-way thermostat;
  • filter of mechanical treatment;
  • The valve, which prevents the formation of countercurrent;
  • reducer;
  • hydro accumulator of diaphragm type with a safety valve;
  • three-way mixing device.

Pay attention! Optionally a countercurrent heat exchanger can be used.

Making a boiler with their own hands

Due to the rather uncomplicated principle of operation, such a device can be made by yourself. Now let’s see how to make an indirect water heater with their own hands.

The whole work of making a water heater consists of assembling the component parts of the structure:

The tank is used as a boiler tank. Its volume depends on the needs of the owners of the house in the hot water and is calculated on the amount of 50-70 liters per person daily. Approximately for a family of 4 people will fit a 200-liter boiler.

For the heating device, the tank must be made of stainless steel, aluminum alloys or other material resistant to corrosion. As an alternative. a gas bottle, but its walls must be cleaned and primed beforehand. Without this action, hot water will have a gas odor.

Five holes are drilled into the tank: two at the side to install the coil, one at the bottom for the inlet pipe, one at the top for water extraction and one at the bottom for the drain cock. When using the boiler outside the heating season, a heating element must be installed. For it also drilled the bottom hole. To the made holes are fastened shutoff elements or ball valves.


For this element is suitable copper or brass tube, the diameter and length of which depend on the volume of the tank. An average of 1.5 kW of thermal capacity per 10 liters of coil tube. A tube of plastic or other metal with a good heat emission can be used.

The tube is spirally wound on a cylindrical mandrel. For this you can take a log or a pipe of large diameter.

When winding the coil it is important to follow the coils:

  • for best contact of heating surface of tube with water to be heated the coils must not touch each other;
  • do not wind the coil with excessive force, then it will not be easy to remove the coil from the mandrel.
  • The number of turns on the coil is calculated from the volume and height of the tank.

Thermal insulation

The outside of the tank should be covered with a layer of insulation. It is necessary to increase efficiency and reduce heat loss. For insulation of the tank is suitable assembly foam, mineral wool or any other insulating material, which is attached to the base with wire, glue or strip ties. For a neat appearance body of the tank is better to cover the thin sheet metal or foil insulation.

The tank can also be heated with another vessel of a larger diameter. For this purpose, the boiler made with his own hands is inserted into a large tank, and the partition is filled with insulation material or foam plastic on the principle of a thermos.

Heating elements for combined BKN

Tubular heaters are available in a variety of building supply stores. To calculate the capacity of the heating element will help the following formula:

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The following values are considered to be calculated:

  • P. heating element power;
  • M. mass of water to be heated;
  • tk. desired water temperature;
  • tn. the initial temperature of the water;
  • T. time of water heating.

The coil in the combined indirect heating boiler is placed over the entire water heating tank from bottom to top. the scheme provides maximum efficiency and uniform water heating. Heating elements are installed at the bottom of the tank.


Assembly of the boiler, made by your own hands, is carried out after the preparation of all components:

  • The coil in the center or along the walls is mounted inside the tank, to its inlet and outlet pipe are soldered spigots;
  • For a vertically standing boiler to the bottom welded supports, for a mounted device. the hinges “ears”;
  • the heating element is installed;
  • The boiler is tightly closed with a lid;
  • Connecting the coil on the scheme of manufacturing indirect heating boiler with their own hands to the heating system;
  • connection of the water inlet/outlet pipe;
  • Piping into the kitchen or bathroom at the extraction point.

How to connect an indirect water heater to a single-circuit boiler

The best position is when the bottom of the hot water tank above the heating boiler and radiators. With recirculation of the coolant If in the presence of a water towel dryer in the system is necessary constant circulation of water through it. In order for the system to function properly you need an accurate calculation of the pump for the indirect heating boiler. There are several ways. Small reservoirs of no more than 15 liters are usually equipped with one heating element of 1.0 kW. This heating element is in direct contact with the water, resulting in limescale deposits that must be removed. Installation options and shapes of boilers There are wall- and floor-mounted boilers, both horizontal and vertical models. That is why it takes so long to heat the water. Hot coil walls transfer heat to cold water, which at the outlet already has a temperature suitable for taking a shower or washing dishes. Control the pressure. At this point the installation is finished. The speed of heating is fully dependent on the capacity of the unit and its volume. Indirect heating boiler


Less often connected to free-standing boilers of similar capacity. The water temperature for the boiler can be set to a value no higher than the temperature of the heat carrier medium by means of a thermostatic head with an integrated sensor. Different boiler strapping diagrams There are several basic ways of strapping the device, which are: With two circulating pumps Both pumps are designed for parallel operation. In normal mode, the upper layer of water in the tank is used first, and it is hotter. We already mentioned the three-way valve. The heated water as required is used for household needs. General requirements In order for the strapping system of a single-circuit boiler with a boiler to work normally, without interruptions and emergencies, the following requirements should be met: An expansion vessel of no less than 10 percent of the boiler volume should be installed at the boiler outlet. Boiler with an indirect heating boiler is connected in the following way: Near the circulation pump cut in the three-way valve. Internal coating of the tank In cheap boilers, the internal coating of the tank is made of enamel or glass ceramics.

Stainless steel. Many single-circuit gas boilers have a summer mode, which will not work for the heating system, and provide heating of the indirect heating boiler. Both have horizontal and vertical models. In this case the electronics of the boiler knows the temperature of the water in the DHW system, and it decides where to direct its power: to heat water in a boiler or to heat.

The boiler is designed so that when the water flow, it is filled with a new portion, and the process continues. Water in the tank can be heated by connecting solar heating systems or heat pumps. Remember about the correct setting of the thermostat!

How to avoid these shortcomings? They differ in their degree of complexity, so you have to choose the best option. That is, in this case, the installation of wall-mounted models is desirable. Ideally, the bottom of the indirect water heater is above the boiler and radiators. Boiler indirect heating device, principle of operation and connection diagram

Examples of popular connection diagrams of a single-circuit gas boiler with a boiler of indirect heating

This is made possible by the use of a separate loop circuit with its own circulation pump. Water is heated enough three-way valve redirects the coolant to the heating system.

It is also very important to reduce heat loss to a minimum, for this purpose the water heater is protected by a special material mineral wool, polyurethane foam, etc.

In this case the flow of the coolant is sent to the heating mains.

If the model is simple, you have to think through a system of temperature control and switching the boiler from heating radiators, to heating hot water. Only an uninterrupted supply of gas or electricity and properly functioning primary heat sources can guarantee the normal operation of the DHW boiler. Therefore, let’s consider, some special types of electric boilers, and how they work, we will give each a small paragraph. Connecting the recirculation ring to a special outlet of the indirector The second disadvantage. recirculation stimulates mixing of water layers.

How to Install a Combination Boiler/Water Heater | Ask This Old House

General principles of operation of an indirect heating boiler

To reduce the time of water heating and for slower cooling of the tank, it is better to choose a model with thermal insulation. Installed with gas appliances with a capacity of 25 kW and above, for the operation of the automatics must be connected to the mains. But this is a topic for a book, not an article.

The disadvantages include the high cost of equipment, do not avoid additional costs if you need to re-equip the existing system. This is a positive point.

This method of fitting is useful for those who use the boiler in a constant mode 2: Variant with two circulating pumps If the boiler is used rarely, for example, seasonally or on weekends, or there was a need for water, the temperature of which is lower than in the heating system, use a scheme with two circulating pumps. Example of installation of a boiler in the bathroom If you choose a storage model of the heater, make sure that the wall will be able to support its weight with water.

connection, diagram, indirect, heating, boiler

There is a temperature sensor and thermostat on the front panel. And its main drawback. it occupies a lot of space. Inside there is a heat exchanger coil. This approach makes it possible to provide hot water to homes, even during periods when boilers or combined heat and power plants do not work. Single-circuit boiler and indirect heating boiler, how to connect?

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